In a microservices system, we might need or want to externalize configuration so that we can abstract sensitive data or credentials outside the applications. We can do something like this with Docker Compose, but the compose file often contains values for multiple services together. We probably want further separation and limited access.
This is where solutions such as Spring Cloud Config come into play. We have a free Neo4j graph database instance on a public cloud, so we can set the credentials in an external location (such as a local file or other systems) and use Spring Cloud Config to access those keys and pass them to the approved application.